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Spin-orbit coupling and electron scattering in high-quality InSb$_{1-x}$As$_{x}$ quantum wells

InSb$_{1-x}$As$_{x}$ is a promising material system for exploration of topological superconductivity in hybrid superconductor/semiconductor devices due to large effective g-factor and enhanced spin-orbit coupling when compared to binary InSb and InAs. Much remains to be understood concerning the fundamental properties of the two-dimensional electron gas (2DEG) in InSbAs quantum wells. We report on the electrical properties of a series of 30 nm InSb$_{1-x}$As$_{x}$ quantum wells grown 40 nm below the surface with three different arsenic mole fractions, x = 0.05, 0.13 and 0.19. The dependencies of mobility on 2DEG density and arsenic mole fraction are analyzed. For the x = 0.05 sample, the 2DEG displays a peak mobility $μ$ = 2.4 $\times$ 10$^5$ cm$^2$/Vs at a density of n = 2.5 $\times$ 10$^{11}$ cm$^{-2}$. High mobility, small effective mass, and strong spin-orbit coupling result in beating in the Shubnikov de Hass oscillations at low magnetic field. Fourier analysis of the Shubnikov de Haas oscillations facilitates extraction of the Rashba spin-orbit parameter $α$ as a function of 2DEG density and quantum well mole fraction. For x = 0.19 at n = 3.1 $\times$ 10$^{11}$ cm$^{-2}$, $α$ $\approx$ 300 meV$Å$, among the highest reported values in III-V materials.